Power actuated master cylinder



Aug- 13, 1963 E. R. PRICE 3,100,379

PowER ACTUATED MASTER CYLINDER Filed 001'.. 24, 1960 Egel. R. Pwcfs' ATTORNEY United States Patent O Filed Oct. 24, 1960, Ser. No. 64,459 2 Claims. (Cl. dll-54.6)

The present invention relates to power operated master cylinders; and more particularly to the type of power operated master cylinder used to actuate the hydraulic braking systems of :automotive vehicles.

\An object of the present invention is the provision of a new and improved construction of a power operated master cylinder which permits lits servomotor unit to be disassembled from the hydraulic section of the unit without disturbing yany of the hydraulic seals within the unit or in the system to which it is attached.

The invention resides in certain constructions, combinations and arrangements of part-s and further objects and advantages .of the invention will become apparent to those skilled in the art to which the invention relates from the following description of the preferred embodiment described with reference to the accompanying drawing forming a part of this specification, and in which:

The solitary FIGURE of the drawing is a longitudinal cross-sectional view of a power operated master cylinder of the type used to actuate the hydraulic braking system on an automotive vehicle, and which unit embodies principles of the present invention.

The power operated master cylinder shown in the drawing generally comprises a hydraulic master cylinder generally designated at A which translates mechanical movement into fluid pressure, and la fluid pressure servomotor B which is suitably affixed to one end of the hydraul-ic master cylinder A. The master cylinder A generally comprises a cast housing having a longitudinally extending bore or chamber 12 therein from .which hydraulic fluid is forced through its outlet 14 -by means of a generally spool-shaped hydraulic piston l16. A hydraulic pressurizing seal is provided by the piston 16 by means of a cup-seal 13 positioned against the inner face of :the piston 16 and which is held in place by means of a retaining washer 24) and a piston return `spring 22. The master cylinder shown is equipped with the usual residual pressure check valve structure generally indicated at 24, which comprises a metallic disc 26 having a rubber membrane `28 stretched over its inner surface and heldin place by thickened peripheral portions 30 which snap over the outer periphery of the disc 26. The membrane 28 is provided with a central opening `32 therethrough, and the disc 26 is provided with a plurality of off-set openings 34 therethrough which are normally closed .ott by the overlying portion of the rubber membrane. Fluid forced out of the cylinder bore 12 passes through the openings 34 to force the rubber membrane away from the surface of the disc, and then passes through its central opening 32 to the Voutlet 14. The inner end of the chamber 12- -is provided with a step surface or yshoulder 36 against which the outer periphery of the rubber membrane 2.3 is Vforced by the piston return spring 22 to provide a check valve mechanism for providing -a back pressure on the iiuid in the system connected to lthe `outlet 14. Return ow through the outlet 14 causes the rubber membrane to rmly close oit the .openings 34 in the disc 26; so that it can only return to the chamber `12 by biasing the check valve structure 24 away from the shoulder 36 to flow around the outer periphery of the disc. The hydraulic master cylinder A further includes a reservoir of compensating fluid 3S positioned in the region overlying the bore 12. A compensating port 40 `communicates the reservoir 38 with the region of the bore 12 just forwardly of 3,100,379 Patented Aug. 13, 1963 ice 2. the cup-seal 18; so that forward movement of the cupseal y18 closes off the compensating port 40, and thereafter pressurizes the fluid in the inner end Iof the hydraulic cylinder or bore '12.

The fluid pressure motor B shown in the drawmg generally comprises a stamped cup-shaped housing 42, and a removable cover plate 44 between'which is sealed the outer periphery of a curtain diaphragm 46 which rforms the movable wall or power piston of the unit. The radially inner end of the curtain diaphragm 46 is clamped between outer andA inner diaphragm plate structures 48 and S0 which transmit mechanical force to the `force transmitting rod S2 which actuates the hydraulic piston 16 of the master cylinder A. The outer diaphragm plate 48 is provided with an outwardly extending boss, and the plates 48 and 50 are cast with suitable chambers and passages therein so that togetherthey form the control valve structure C for the servomotor.

The servomotor B, shown, is an atmosphere suspended unit in which the innerand outer power chambers 54 and 56 respectively positioned on opposite sides of the diaphragm structure are normally supplied with atmospheric pressure, and in which vacuum is communicated the inner power chamber 54 to actuate the unit. The control valve structure C generally comprises an inner movable vacuum valve seat 5S that is positioned generally concentrically inwardly of an annular vacuum valve seat 60-1both of which seats face inwardly and are adapted to be closed oir" by a movable poppet member 62. The outer Vacuum valve seat 60 is formed integrally on an inner partition in the outer diaphragm plate 48; and the poppet member 62 is afiixed to and carried by a rubber diaphragm 64 which is sealingly clamped between the diaphragm plates 48 and 50 to form the vacuum valve chamber 66 of the control valve.

Atmospheric pressure is continually communicated to the outer power chamber 56 by a suitable opening, Vnot shown, in the cover mem-"oer 44; and the atmospheric pressure in chamber 56 is transmitted through the atmospheric passageway 68 to the region lying behind the diaphragm 64, and thence ows through the central .opening of the poppet member 62 to the atmospheric Valve seat 58. The region between the vacuum valve seat 60 and atmospheric valve seat 58 forms the control chamber 72 of the valve, and is communicated to the inner power chamber 54 through the control passageway 7 4. The atmospheric valve seat 58 is formed as an integral flange on the axially positioned control member 7 6 which is `suitalb-ly guided `for inward movement by the push rod 78; and the push rod 78 in turn is actuated by means ofthe usual brake pedal lever of an automotive vehicle.

In the position Iof the control valve )se-at shown in the drawing, atmospheric pressure flows from the outer chamber S6 through the passageway 58 and chamber '70 to the atmospheric valve seat 58. Inasmuch as the valve seat 58 is out of engagement with the puppet member 62, atmospheric pressure is free to tiow past the valve seat to the control passageway 74 leading to the inner power cham-ber 54; thereby Iestablishing atmospheric pressure on both sides of the movable wall of the unit. Inner movement of the push rod 78 causes the atmospheric valve seat 5S to abut .the poppet 62 and thereafter close oit further communication of the atmospheric pressure to the inner power chamber 54. Further inward movement ot the push rod 7 8 causes the atmospheric valve seat `58 to lift the poppet member `621 out of engagement with the vacuum valve Iseat 60, and thereby communicate vacuum to the control passage 74 and inner power chamber 54. Vacuum from the manifold of the vehicles propelling engine is continually communicated to the vacuum chamber 66 through the flexible vacuum tube 80, so that the pressure in the inner power chamber 54 is thereby a *i Y reduced. Differential pressure across the movable wall causesvthe movable wall .tomove inwardly, and thereby actuate the hydraulic piston i of the master cylinder.

` f Inorder that ,a reactive forceiwill be produced upon the push rodvnyhich Ais' generally proportional `to the pressure vthat yis :developed by the master cylinder A, vthe i inexpensive to build than p' ton type. movable walls, but

they have the'dilhculty of not providing ya support for themselves relative to the housing of the servomotor. In vacuum suspended lservomotors there is provided a sealing tube which projects from the movable wall through the t cover plate .alito seal off theouter chamber S6 from the inner face'of the inner diaphragmrplate 5a is providedY withv a' reaction chamber S2.' The inner end of the reaction chamber 82 .is closed oi'by a cylindrical head 84 onthe force transmitting rod 52, `and a block ofY rubber like material A86 is positioned betweenrthe head Se and the 'bottom ofthe reactionV chamber 82.v Force that is exerted upon the movable Wall of the servomotor B is applied to the. outer face of the block do of rubber like material toin turn pressurize .the rubber and force it against the cylindrical head S4 of pushrod 52. In order that a reactive force will be provided to the push rod 7S, theV inner end of the control member 76 is provided with asmall diameter boss 88 which extends through a small opening 90 in ,the diaphragm plate 5b to engage the outer face fof the rubber-reaction disc 85. A percentage of the Y force applied to -tllerubber reaction disc Se is'therefore transmitted rearwardly; to -the foot of the operator.

rkForce applied to the' yforce transmitting rod 52 causes the hydraulic piston 16 to move past the compensating 'port- -50 to thereafter force fluid out of .the hydraulic chamber 12 into the braking system` Vwhich :it actuates. When a desired effort has been achieved, inward movementV of the push rod 78Wis stopped by the operator;

' whereupon the movablerwall moves inwardly a slight amount to bring the vacuum valve yseat o@ again into engagement with the poppet member l62 and thereby preventV further pressure differential buildup-across the movable wall. When it is desired Vtoreduce` the braking effort,

the force applied to the push rod 78 is reduced; whereupon the pressure forces on the rubber reaction disc 86 forcesthe control member-76 rearwardly to V4litt the atmospheric valve seat 5S out ,of engagement withV the poppet d2" to thereby decrease the pressure in the inner power cham- `ber 54. The hydraulic pressure in the chamber 22 as Well as the power piston return spring 92 causes the movable lwall to move rearwardly land thereby follow the retractile movement of' the pushY rod 73 until the retractile movement is stopped. Thereafter, the movable wall moves rearwardly a slight additional 4amount to brinfr the poppet 4member `62 into engagement with kthe atmospheric valve seat 58, and thereby prevent further increase in pressure Vin the inner power chamber 54. With the valve structure in this closed position, the 'brakes are held applied with a force generally proportional thatdeveloped by the servomotor B; and should it be desired toi completely release the brakes, all force is removed Afrom the push rod 78. This permitsv the valve return spring 94 to hold the atmospheric'poppet 58 out of engagement wit'njthe poppet' member 62, to thereby permit fullatmospheric pressure to be obtained in the inner power chamber Se, and the movable Wall to move toits fully-,retracted position shown in the drawingl' f Y 57 Thetdiaphragm `64 4foritheV pioppet member is sized so that atmospheric to vacuum dieren-tial `subsftantailly oisets .the pressure force tending to unseat the poppet 62 from thevalveseat 60, and :a puppet biasing spring 95 is used to assure tight sealing engagement with the respective valve Yseat 60jand 58. An adjustable stop member 98 is threaded into the end cover member 44;- for abutment by ,theA movable wall to limit the retraction of the Vmovable parts ofthe un-it to a position wherein the lip of the seal 18 is just rearwardly of the compen-satingport dil.v As previously' indicated it has been ari-object of the present invention to provide an overall power operated V`master cylinder construction which will be very inexpensive to manufacture and which Vwill permit the servo- Vmotor unitl to be separated from the hydraulic structure of` then-nit without removing or changing any of the li'ydrauli-c parts. Diaphragm type movable walls are more atmosphere; andV so in this type Vof unit a suitable guide Vstructure is of necessity provided Vwhich will permit the use :of 'a diaphragmistructure-such as the curtain diaphragm 46 shown in the drawing.V Atmospheric suspended units, such Vas the one shown in the drawing do not have such guide structure, southat the problem of how to support Vva diaphragm type movable wall in an atmospheric i' suspended servomotor-unit has (existed in the art for a unit B is removed from the master cylinder A. ln order that the'movable wall can be supported from the hydrauiic piston 16, the push rod receiving chamber ll02V of the hydraulic piston 16 must lbe provided with a 'surface adjacent its outer end which tightly engages a companion Vsurace on the force transmitting rod 52. In order that a tight sliding iit between these surfacesrcan be assured even though mass production methods are used, these Isuriacesshould preferably be cylindrical so that tolerances-in the length of the force transmitting rod, and the depth of the hole,V will not produce a variation in the Vclearance between the abutting surfaces.' In the preferred embodiment shown in the drawing, the outer section ldd of lthe chamber` 162 is made cylindrical, and the force vtransmitting rod 52 is provided with a corresponding Vcylindrical surface, so that -it will have a close sliding iit` rod 52 is closely engaged bythe inner Vend of the chamber n 52 are made spherical.

1&2. ln the kembodiment shown in the drawing, the inner ends of the chamber 192 and force transmitting rod It will therefore be seen that the force transmitting rod 52 is tightly engaged. by the piston 16 at spaced points so that it adequately supports the movable element of the servomotor unit B. Appli- Icant is aware that spool-shaped hydraulic pistons have been used in master cylinders before; but these spoolshaped pistons have never had a load cantilevered and supported therefrom. All of the prior lart spool-shaped pistons with which I am aware have had -insuiiicient bearingarea 106 outwardly of ,their secondary seal 168 to adequately support a cantilever load. By providing an adequate bearing larea 106 in the region generally overly- -ing Athe cylindrical surface 104 it has been found that Ythe movable wall structureof a servomotor can be satisfactorily cantilevered from a spool-shaped hydraulic piston in the hydraulic chamber of a master cylinder.

While the invention has beenrdescribed in considera-ble detail, I donot nvish -to be limited to the particular consti-notions shown andv described; and it is my intention to cover hereby Aall novel adaptations, modifications and arrangements thereof ywhich come within the practice of those skilled in the art to which the invention relates.

. end surface of said housing, a longitudinally extending pistonpositioned in saidichamber, said piston having penipheralsurfaces adjacent its opposite ends which slidingly abut the sidewalls of said chamber, said piston :also having an axially extending opening communicating with the outer end of said piston and the sidewalls of said opening being cylindrical adjacent the outer end of said opening, a servomotor having a housing which is axially aligned and `fastened to said outer end of said master cylinder housing, a force transmit-ting rod having an inner end in Kabutment lwith the inner end of said opening in said piston and a spaced cylindrical peripheral surface engaging said cylindrical surface of said opening adjacent said outer end of said opening, and a exible movable wall in said se-rvomotor supported relative to said fluid pressure motor housing by said force transmitting rod, whereby said iiuid pressure motor can be removed from said master cylinder housing without brealrin-g the seal of said piston in said fluid pressurizing chamber.

2. A power operated master cylinder construction cornprising: a master cylinder housing having an axially ex- -tending uid pressurizing chamber opening into an outer end surface of said housing, a longitudinally extending piston positioned in said chamber, said piston having peripheral surfaces adjacent its opposite ends which slidingly abut the sidewalls of said chamber, said piston 6 also having an axially extending opening communicating with the outer end of said piston and the sidewalls of said opening being cylindrical adjacent trhe outer end of said opening, a servornotor having a housing which is axially aligned and vfastened Ito said outer end of said master cylinder housing, 4a force transmit-ting rod having an inner end in abutment with the inner end of said opening in said piston and a spaced cylindrical peripheral Y References Cited in the le of this patent UNTED STATES PATENTS 2,373,272 Stelzer Apr. 1-0, 1945 2,968,155 Kellogg et al. lan. 17, 1961 3,016,880 Kellogg et al. lan- 16, 1962 

1. A POWER OPERATED MASTER CYLINDER CONSTRUCTION COMPRISING: A MASTER CYLINDER HOUSING HAVING AN AXIALLY EXTENDING FLUID PRESSURIZING CHAMBER OPENING INTO AN OUTER END SURFACE OF SAID HOUSING, A LONGITUDINALLY EXTENDING PISTON POSITIONED IN SAID CHAMBER, SAID PISTON HAVING PERIPHERAL SURFACES ADJACENT ITS OPPOSITE ENDS WHICH SLIDINGLY ABUT THE SIDEWALLS OF SAID CHAMBER, SAID PISTON ALSO HAVING AN AXIALLY EXTENDING OPENING COMMUNICATING WITH THE OUTER END OF SAID PISTON AND THE SIDEWALLS OF SAID OPENING BEING CYLINDRICAL ADJACENT THE OUTER END OF SAID OPENING, A SERVOMOTOR HAVING A HOUSING WHICH IS AXIALLY ALIGNED AND FASTENED TO SAID OUTER END OF SAID MASTER CYLINDER HOUSING, A FORCE TRANSMITTING ROD HAVING AN INNER END IN ABUTMENT WITH THE INNER END OF SAID OPENING IN SAID PISTON AND A SPACED CYLINDRICAL PERIPHERAL SURFACE ENGAGING SAID CYLINDRICAL SURFACE OF SAID OPENING ADJACENT SAID OUTER END OF SAID OPENING, AND A FLEXIBLE MOVABLE WALL IN SAID SERVOMOTOR SUPPORTED RELATIVE TO SAID FLUID PRESSURE MOTOR HOUSING BY SAID FORCE TRANSMITTING ROD, WHEREBY SAID FLUID PRESSURE MOTOR CAN BE REMOVED FROM SAID MASTER CYLINDER HOUSING WITHOUT BREAKING THE SEAL OF SAID PISTON IN SAID FLUID PRESSURIZING CHAMBER. 